In 1903 a deposit of gypsum was discovered on the site of the present Fort Dodge Plant. This was not startling because people at that time knew the Fort Dodge gypsum bed was one of the most extensive in the country. What was unusual was the Plymouth mill, the biggest plaster mill in Iowa was built there.

Mining operations continued near the mill until 1906 when the rock supply was exhausted. A new mine was opened on the west side of the Des Moines River. No bridge spanned the river at that time so an aerial tram line two and a half miles long was built to transport rock from the mine to the plant. Each car carried 1000 pounds of crushed rock, riding on cables suspended in the air. The tram line was dismantled in 1947.

Fort Dodge started to acquire the know-how of wallboard production during World War I when a board plant was built alongside the Plymouth mill. Until that time, the gypsum was used primarily as wall plaster, insulation material, fertilizer, and as a retarder for Portland cement. As wallboard, gypsum became an economical substitute for wood.

Making wallboard was a slow, tedious process. It had to be taken by hand from the setting belt; hung on racks, and placed in the kiln to dry. Lath was the result of sawing wallboard into 16 x 36-inch pieces.

The Fort Dodge plant took a new lease on life in 1935 when it began manufacturing Gold Bond products. Two years later, a new board plant was constructed on the site of the original Plymouth mine. Next, a plaster warehouse was built and equipped with the latest type of mixing and bagging equipment. Then, early in September 1937, a fire practically wiped out the old, wooden mill building. Soon afterwards, a new mill was built to supply stucco for the board plant and plaster warehouse. At the same time, a new office, store room, machine shop and change house were constructed.

The gypsum deposit, which for nearly forty years had supplied the plant with rock, began petering out in 1944. A quarry was opened a mile south of the plant. The old mine, with its overhead tram line, was closed on June 2, 1947.